The present invention relates to a process for producing semiconductor chips from a semiconductor wafer and, more specifically, to a process for producing a large number of semiconductor chips from a semiconductor wafer having a large number of rectangular areas defined by streets arranged on the surface in a lattice form, semiconductor circuits being formed in the respective rectangular areas.
As known to people of ordinary skill in the art, in the production of semiconductor chips, streets are arranged on the surface of a semiconductor wafer in a lattice form to define a large number of rectangular areas, and semiconductor circuits are formed in the respective rectangular areas. Then, the back surface of the semiconductor wafer is ground to reduce the thickness of the semiconductor wafer to a predetermined value. Thereafter, the semiconductor wafer is cut along the streets to separate the rectangular areas from one another to obtain semiconductor chips.
The production of semiconductor chips in the prior art, however, has the following problems to be solved. That is, the grinding of the back surface of the semiconductor wafer is generally carried out by applying a rotary grinding wheel to the back surface of the semiconductor wafer. The rotary grinding wheel comprises a grinding means containing diamond grains, and this grinding means has a substantially flat grinding surface which is pressed against the back surface of the semiconductor wafer. When the back surface of the semiconductor wafer is ground, a cooling liquid such as pure water is jetted over the area to be ground. However, since the grinding surface of the grinding means is substantially flat, the cooling liquid cannot be jetted over the area to be ground sufficiently, and an undesired burn may be formed on the ground back surface of the semiconductor wafer. Further, chippings may not be discharged well from the area to be ground, thereby causing reduction of grinding efficiency.
Further, the cutting of the semiconductor wafer along the streets is generally carried out by applying the rotary cutting blade to the front surface of the semiconductor wafer. At this time, fine chippings may be formed on the back surface of the semiconductor.
It is therefore the principal object of the present invention to enable to grind the back surface of a semiconductor wafer fully effectively by preventing and suppressing the formation of a burn on the back surface.
It is another object of the present invention to prevent and suppress the formation of chippings on the back surface of the semiconductor chip when a rotary cutting blade is applied to the front surface of the semiconductor wafer to cut the semiconductor wafer along the streets.
According to the present inventor, the above principal object can be attained by a process for producing a large number of semiconductor chips from a semiconductor wafer having a large number of rectangular areas defined by streets arranged on the surface in a lattice form, a semiconductor circuit being formed in each of the rectangular areas, wherein
a plurality of grooves having a predetermined depth are formed in the back surface of the semiconductor wafer, then
the back surface of the semiconductor wafer is ground to be reduced the thickness of the semiconductor wafer to a predetermined value, and thereafter,
the semiconductor wafer is cut along the streets to separate the rectangular areas from one another to obtain semiconductor chips.
In a preferred embodiment of the present invention, the grooves are formed by cutting the semiconductor wafer to a predetermined depth from the back surface with the rotary cutting blade, a grinding means having a substantially flat grinding surface is applied to the back surface of the semiconductor wafer to grind the back surface of the semiconductor wafer, and a rotary cutting blade is applied to the front surface of the semiconductor wafer to cut the semiconductor wafer along the streets. The another object is attained by forming the grooves corresponding to the streets in such a manner that the grooves have a depth larger than the grinding depth of the back surface of the semiconductor wafer and the grooves are still existent even after the back surface of the semiconductor wafer is ground. The width of the grooves is preferably larger than the cutting width at the point when the semiconductor wafer is cut along the streets.